The present invention concerns a low voltage electric power transmission and distribution system, such as prefabricated electrical trunking, including transmission components constituted by several parallel, insulated conductors laid against each other, associated with distribution components, constituted by several parallel conductors spaced apart from each other.
Systems for transmitting and distributing electric power by prefabricated electrical trunking are well known. Their function is on the one hand to transmit electric power from one position to another within an installation, for example from one electrical control board to another electrical control board, and on the other to distribute this electric power in respect of the different receivers spread in location within this installation, by offering fixed connection points at close intervals all along the trunking, for example of the order of one or two connection points per meter. The receivers are then supplied by means of tap-off junctions at these connection points. Moreover requests are often made for a tap-off junction to be installed or removed easily without cutting off the electricity supply in the trunking according to a type of connection known hereinafter as a xe2x80x9cplug-inxe2x80x9d.
There is a first technology for manufacturing such prefabricated electrical trunking wherein the conductive trunking bars are parallel to, insulated from and laid against each other within a metal sheath. This first technology allows the reactance of the prefabricated electrical trunking to be reduced and brings a better thermal exchange with the outside particularly for strong currents, such as those above 1000A. In a second technology, the conductive bars are parallel but spaced apart from each other in the sheath. This second technology increases the reactance of the electrical trunking and renders the thermal exchange with the outside less effective, but it does make it much easier to install and remove tap-off junctions according to a xe2x80x9cplug-inxe2x80x9d type connection. The first technology is therefore well adapted for the electric power transmission function whereas the second technology is better adapted to the electric power distribution function.
One solution therefore consists in using conductive bars which are insulated from and laid against each other but open out at regular and close intervals to offer xe2x80x9cplug-inxe2x80x9d type connections. However, in this solution, outward heat dissipation becomes less efficient and the cost of such trunking goes up fast when the power is high particularly given the difficulty in insulating and folding large conductive bars at close intervals. In the solution disclosed in U.S. Pat. No. 4,886,468, electrical trunking is constituted by insulated conductive bars, laid against each other and having at regular intervals conductive outgrowths, transverse to the longitudinal axis of the bars and separate from each other so as to allow a connection in respect of xe2x80x9cplug-inxe2x80x9d type tap-off junctions. Heat dissipation along the trunking occurs effectively since the bars remain laid against each other but such a system remains complex to manufacture and insulate. Moreover by reason of their construction, these solutions systematically offer connection points over the whole length of the trunking even in areas of the installation where the user has no tap-off junction to install, which may provide him with points far in excess of his real need.
The purpose of the invention is therefore to propose an electric power transmission and distribution system having concurrently the technical and economic advantages of both technologies and therefore providing on the one hand the transmission function with low circuit impedance, small losses and good heat dissipation and on the other hand the distribution function with xe2x80x9cplug-inxe2x80x9d type connection possibilities, while optimising the number of these connection possibilities as a function of the real needs of the user.
To this end, the invention describes an electric power transmission and distribution system including several transmission components, each having several parallel, insulated transmission conductors laid against each other, each end of these transmission components having an opening out of the transmission conductors to connect two adjacent transmission components by means of a terminal block, and including at least one distribution component having several parallel distribution conductors spaced apart from each other, one at least of the two ends of which is directly connected to a transmission component by a tap-off device at terminal block level, with no additional means of electrical protection against current overloads.
The cross-section of the distribution conductors is smaller than the cross-section of the transmission conductors. A limited number of tap-off points, spaced out at intervals, are provided along the distribution components, allowing tap-off junctions to be installed by xe2x80x9cplug-inxe2x80x9d type connections. The total current consumption of receivers connected to the tap-off junctions of a distribution component may be greater than the rated current running uniformly through the length of a distribution component.